1. Field of the Invention
The present invention mainly relates to a ventilation fan.
2. Description of the Related Art
A ventilation fan is a common ventilating device. Sometimes the ventilation fan is provided onto a frame of a ceiling so as to draw out the indoor air. In that case, the weight of the ventilation fan is usually managed to be reduced in view of the safety weight that can be withstood by the ceiling.
As shown in FIG. 1, a ventilation fan 100 comprises a frame 1, a scroll casing 2 provided in the frame, and a motor 3. The motor 3 is fixed on an opening portion of the scroll casing 2 by means of a motor holder 7 which is formed integrally with the scroll casing 2, and fan blades 5 are mounted on the motor 3. Once the fan blades 5 rotate, a negative pressure is generated in the scroll casing 2 so as to draw in air.
The frame 1 is usually made of metal materials in order to obtain integral sturdiness. The scroll casing 2 and the motor holder 7 are made of resin materials, thus the weight of the ventilation fan 100 may be reduced.
If the motor 3 operates for a long time, a large amount of heat will be generated. Though the above design reduces the weight of the ventilation fan 100, the heat can not be emitted effectively, which results in a rise in temperature of the motor 3. The rise in temperature may deform the motor holder 7 fixing the motor 3 and thus causing the motor 3 to depart from an original mounted position. As a result, the performance of the ventilation fan 100 deteriorates, and more adversely, the fan blades 5 may come into contact with the scroll casing 2 and thus the ventilation fan 100 may be damaged.
However, it is very difficult to provide a heat dispersion structure for the motor 3 alone due to the limitation of an inner space of the ventilation fan 100.